1. Field of the Invention
The invention relates generally to systems for reading meters and more particularly to a method and an apparatus for automatically reading a utility meter by optically reading a shadow of a meter pointer that falls on a meter face.
2. Description of the Prior Art
Meters are commonly used by utility companies for measuring and providing a readout for the quantity of water, gas, or electricity that has been used in a commercial or residential establishment. Historically, the meter readout is read by a person who walks or drives from establishment to establishment and then reports the readings to an office. Such process is labor intensive, subject to human error, and in certain circumstances may not be safe for the person. In order to eliminate these problems, automatic reporting meters have been developed that integrate the capability of measuring the amount of water, gas, or electricity with the capability of communicating the measurement to the office using either wired or wireless signal transmission. However, reporting meters are generally limited by economics to new meter installations. In order to improve the economics for existing utility meters installations, several meter reader interfaces have been developed or proposed that retrofit to an existing meter. These meter reader interfaces automatically read the position of the meter pointer with respect to the meter face using optics and communicate the meter reading in a signal transmission. Typically, the optical frequency that is used is in the infrared range because optical components are least expensive in that range. Unfortunately, the reflection coefficient of the pointer and the reflection coefficient of the face in the infrared range are not greatly different in certain meters thereby decreasing the reliability with which the meter can be read.